OBJECTIVE The aims of our study were to determine on the one hand a correlation between the presence of anti-Helicobacter pylori (anti-H. pylori) IgG antibodies in serum and cervical mucus of women with idiopathic infertility, and on the other hand the effect of these antibodies on cervical mucus quality, in particular related to the ability of spermatozoa to penetrate it. METHODS We analysed anti-H. pylori IgG antibodies in the serum and cervical mucus of 67 patients diagnosed with idiopathic infertility using the Quanta Lite H. pylori IgG test. The penetration of normal sperm, in 15 cervical mucus samples positive for anti-H. pylori antibodies and in 15 negative samples, was assessed using the simplified slide test. RESULTS A significant positive correlation emerged between anti-H. pylori IgG antibody concentrations in the serum and in the cervical mucus (r=0.9275; p<0.00001). In the 15 anti-H. pylori IgG mucus-positive samples the slide test showed abnormal penetration by the spermatozoa. CONCLUSIONS Our study demonstrated that the presence of anti-H. pylori antibody in the cervical mucus can be involved in female infertility, interfering with sperm progression. Considering the close correlation found between serum and cervical mucus anti-H. pylori antibody titres, measuring serum antibodies could become an additional test, in particular in couples with unexplained infertility.